The present invention relates to systems for controlling venting of fuel vapor from a vehicle fuel tank, and particularly to a vent valve in a fuel valve tank venting system. More particularly, the present invention relates to a tank valve which prevents liquid fuel within a fuel valve tank venting system from entering and contaminating a vapor recovery canister within the system.
Significant quantities of fuel vapor can escape from a fuel tank and out to the atmosphere during the refueling of motor vehicles. Early attempts to control the vapor escape focused upon control devices fitted to a fuel dispensing pump nozzle connected to a service station fuel pump. Later, control devices mounted directly on board the vehicle were developed. See, for example, U.S. Pat. No. 4,816,045 to Szlaga et al. relating to a vapor recovery system mounted on the fuel tank filler neck. Tank venting systems which mount to a fuel tank have also been developed as shown, for example, in U.S. Pat. No. 5,156,178 to Harris. Typical vehicle fuel tanks often contain a valve, or a set of valves, mounted to the top of the fuel tank which vent fuel vapor to a vapor-recovery canister during refueling, thereby preventing the vapor from escaping to the atmosphere. When the liquid fuel level within the tank nears the top of the tank, the valve or set of valves, floats closed causing a pressure xe2x80x9cback-upxe2x80x9d to the fuel dispensing nozzle. A sensor within the nozzle senses this xe2x80x9cback upxe2x80x9d and causes the nozzle to shut off before the tank is over-filled.
After refueling, vehicle operation causes the fuel level within the tank to subside. The tank vent valves, therefore, reopen and any fuel vapor that is generated in the fuel tank during operation of the vehicle (e.g., by evaporation or by sloshing of the liquid fuel against the walls of the tank) is carried by a fuel vapor conduit to a vapor recovery canister. Excessive sloshing or high pressure within the fuel tank can cause xe2x80x9cliquid carryoverxe2x80x9d wherein liquid fuel escapes past the valves and travels to the vapor recovery canister along with fuel vapor. Liquid fuel within the vapor recovery canister contaminates the canister rendering it ineffective. Mechanisms to prevent liquid from escaping to the vapor recovery canister through the tank valves would help to prevent contamination of the canister.
According to the present invention, a tank vent valve includes a valve container coupled to a valve lid adapted to be mounted to a vehicle fuel tank. The interior of the vent valve is partitioned into three chambersxe2x80x94a float chamber, a primary liquid separation chamber, and an auxiliary liquid separation chamber. A float valve assembly is positioned within the float chamber and is operable between an opened and closed position. In its closed position, the float valve prevents fuel vapor from escaping from the fuel tank through the vent valve. A canister nipple is formed in the valve lid and defines an outlet port from the auxiliary liquid separation chamber to the vapor-recovery canister. Opposite the canister nipple, and also formed as part of the valve lid, is an inlet nipple defining an inlet port from a second vent valve mounted to the fuel tank at a different location to the auxiliary liquid separation chamber.
A diversion baffle is positioned in the lid chamber and between the inlet port and the outlet port to create an obstacle preventing direct flow from the outlet port through the lid chamber to the inlet port.
A baffle is provided to separate the primary liquid separation chamber from the auxiliary liquid separation chamber. The baffle serves to redirect and block liquid flow escaping through a venting outlet. In this way, liquid fuel is prevented from flowing to and through the outlet port.
In preferred embodiments, the valve lid is molded to include a cover dome which defines the lid chamber. Further, molded inside the cover dome is the diversion baffle. In one embodiment, the diversion baffle includes a front wall and two side walls and a downwardly-facing opening to the lid chamber.
In preferred embodiments, the baffle provides a protector floor within the valve container which separates the primary liquid separation chamber from the auxiliary liquid separation chamber. The protector floor is formed to include multiple apertures. Further, the baffle is formed to include several legs, also arranged around the perimeter, which serve to maintain the baffle in spaced apart relationship with the valve lid.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.